Tension levelling of strip

ABSTRACT

The disclosure of the invention pertains to a method and apparatus for producing flat rolled steel strip by tension levelling. The unflat strip is subject to varying tensions by a pair of tension bridles. Between the bridles are arranged two sets of nested, flexing and/or rolling rolls and on the entry and delivery sides of the roll sets are arranged strip deflecting rolls which are both skewable and mechanically shapeable to vary the unit tension of the strip during its flexing and/or rolling. Also on the entry and delivery sides of the sets of flexing rolls are strip shape detecting rolls which are associated with a computer control unit that produces both feed forward and/or feed backward control signals for varying the total tension, the flexing and/or rolling, and the unit tension to give the most ideal processing conditions for a strip of given characteristics.

Greenberger 1 1 1974 [5 1 TENSION LEVELUNG 0F STRHP 3,605,470 9/1971Polakowski 72/163 [75] Inventor: $1 2223? lgaGreenberger PrimaryExaminer-Milton S. Mehr Attorney, Agent, or Firm-Henry C. Westin; Daniel[73] Assignee: Wean United Inc., Pittsburgh, Pa. Pat h 22 Filed: Nov. 61972 1 s [57 ABSTRACT [2]] Appl' 3047182 The disclosure of the inventionpertains to a method and apparatus for producing flat rolled steel stripby [52] 11.3. (I1 72/17, 72/205, 72/161 tension levelling. The unflatstrip is subject to varying [511 lint. C1 821d 1/02 tensions by a pairof tension bridlles. Between the bri- [58] Field of Search 72/ 160, 165,205, 17 dles are arranged two sets of nested, flexing and/or rollingrolls and on the entry and delivery sides of the [56] References Citedroll sets are arranged strip deflecting rolls which are UNITED STATESPATENTS both skewable and mechanically shapeable to vary the s unittension of the strip during its flexing and/or roll- ?82125? 3/132;831E321?""""'iiiiiiiijijijf'ii 3 215 Also on she ssssy sss sslivssysides sf shs ssss sf 332531445 5/1966 Franeku... 72/205 x flexing rollsare Strip Shape detecting 10115 which are 3,324,695 6/1967 Sirilotti 72/15 associated with a computer control unit that produces 3,326.0266/1967 Guillot i v. 72/163 both feed forward and/or feed backwardcontrol sig- 3,328,992 7/1967 Stone i 72/250 X nals for varying thetotal tension, the flexing and/or 311374343 9 y 72/205 rolling, and theunit tension to give the most ideal pro- 3s459s0l9 3/1969 Stone s s scessing conditions for a strip of given characteristics 3,499,306 3/1970Pearson i 72/17 3,527,078 9/1970 Lawson et al 72/160 21 Claims, 4Drawing Figures 2a a: a0

TENSION LlEVELLING OF STRIP Though many different attempts have beenmade in the past in the metal industry to produce flat strip in aneconomical high production manner only partial success has beenachieved. One of the reasons for this failure has been the fact that thecharacteristics of the strip, such as thickness, physical properties,and metallurgy vary considerably not only from strip to strip but withina given strip itself.

While tension levelling employing nested flexing rolls has beensuggested in the past their success as best has only been rudimental,because on the one hand the work capable of being performed was notsufficient to meet the varying conditions, and on the other hand theprocedures of controlling the working forces was very uncoordinated andineffectual.

It is therefore an object of the present invention to provide a methodand/or apparatus for producing flat metallic strip that will overcomeamong others the enumerated disadvantages and limitations of priorpractices.

More particularly the present invention provides a method and apparatusfor producing flat metallic strip at an efficient and high productionrate including the steps and apparatus of subjecting the strip to asubstantial total tension but below its yield point, causing the stripwhile under said tension condition to pass between a series of stripflexing rolls where the strip is additionally subjected to reverseflexing sufficient to impart a relatively small amount of permanentelongation to the strip, varying the unit tension transversely of thestrip in a manner to vary the transverse unit tension of the portion ofthe strip being subject to the flexing operation, determining thetransverse flatness profile of the strip and changing at least one ofsaid total tension, flexing or unit tension operations to reducenonflatness in the strip.

These objects and other novel features and advantages of the presentinvention will be better appreciated when the following description of apreferred embodiment thereof is read along with the accompanyingdrawings of which:

FIG. I is an elevational view, partly in section, of an arrangement ofequipment for practicing the present invention,

FIG. 2 is a plan view of FIG. I

FIG. 3 is a schematic enlarged elevational view, partly in section, ofsome of the equipment illustrated in FIG. 1 and wherein the stripflexing units are shown in their rolling and flexing positions and FIG.4 is a partial view of one of the strip flexing units illustrated inFIG. 3 shown in a strip flexing position.

In referring to FIGS. I and 2 a rolled carbon steel strip is shown, thetwo arrows indicating the entrance and delivery of the strip to atension levelling zone of a strip processing line. At the entrance anddelivery cnds of the zone there are arranged identical strip tensionbridle units 12 and I4 each having a entry set of horizontallyspaced-apart driven rolls l6 and 18 from where the strip 10 passes to adelivery set of similar driven rolls 20 and 22. The rolls 18 and 20cooperate with pinch rolls 24 which are vertically adjusted by pistoncylinder assemblies 26. Bridle units of the type illustrated are wellknown in the steel strip producing industry so that the details of theirfunctions and operations are not deemed necessary. Sufficient is to notethat they are employed, by virtue of a speed differential and the wrapangle between the cooperative sets of rolls 16-18 and 2022, to subjectthe strip I0 to substantial total tension up to the yield point of thestrip, and that the total tension is variable by changing the powerfurnished to the roll sets. In the case of mild carbon rolled steelstrip 48 inches wide and having a thickness of 0. 125 inch a desirableoverall operating tension would be of the order of 60,000 lbs. totaltension.

Between the entry roll set 20 and 22 and the delivery roll set 16%8 twosets of flexing or flexing and rolling rolls are provided, the entry setbeing identified at 28 and the delivery set at 30, both of which arerotatably supported in a common housing 32.

Roll set 28 comprises an upper quickly adjustable backup roll 34 whichengages a smaller diameter nested roll 36, the lower surface of whichengages one surface of the strip while the opposite surface of the stripis engaged by two larger diameter rolls 38 and 40. As best shown inFIGS. 3 and 4- the backup roll 34 which is carried at each of itsopposite ends by a bearing chock assembly 42 is vertically positionedagainst motor operated screw stops 44 associated with each chockassembly, by virtue of piston cylinder assembly one being shown at 46,which is shown only in FIGS. I and 2. The screw stops 44 and pistoncylinder assemblies 46 permit the nested smaller roll 36 to vary itspenetration into the space between the rolls 38 and 40 from a rollingcondition where the strip is both flexed and compressed by rollingbetween the rolls 36 and 38 and 40 to only a pure flexing action wherethe roll 36 is spaced from and out of direct contact with the rolls 38and 40. FIG. 3 is meant to portray the flexing and rolling conditionwhere the total permanent elongation imparted by these forces will notexceed 2 to 4 percent while FIG. 4 portrays the pure flexing conditionwhere the total .permanent elongation will be less than 2 percent. Adesirable roll size range for various carbon steels will find the largerolls 34., 38 and 40 being of a diameter between 12 to 14 inches and thesmall nested roll 36 having a diameter of between 3 to 6 inches.

The rolls of the flexing or flexing and rolling set 30 are identical butinverted with respect to the roll set 28, in which as shown in FIG. 3the upper larger rolls 4% and 50 are vertically positioned by pistoncylinder assemblies 52 against motor operated screw stops 54 for thepurpose already explained with respect to the roll set 23.

On the entry and delivery sides of the roll set 28 and 30 there arearranged transversely of the path of the strip strip engaging rolls 56and 58 rotatably sup,- ported in the housing 32. The roll 56 is arrangedto engage the upper surface of the strip while the roll 53 en gages thelower surface. As shown by the legends and arrows in FIG. 3 the rolls 56and 58 are vertically tiltable and which is indicated in legend in FIG.3 as ROLL TILTING. The rolls are also mechanically shaped to change thecrown which is legend ME- CHANICAL ROLL SHAPING and/or to have theirends moved in a horizontal plane whis is legend SKEW- ING in FIG. 3. Theresult of tilting, mechanical shaping and skewing, as is well known inthe art, is to vary the unit tension of the strip in the roll bite ofthe roll units 28 and 30. In other words in changing the crown of rolls56 and 58 and/or its end to end position, in which the roll is rotatedabout its minor axis, a greater or less unit tension can be brought intoplay transversely of the strip as it is being worked in the roll setunits 28 and 30, by virtue of varying the lengths of the paths of travelof different portions of the strip width. Since the use of stripdeflecting rolls in which the crown of the rolls may be varied byoutboard bending forces or skewing or tilting end to end by power meansare well known details of construction need not be given.

Also mounted in the housing 32 at its extreme outer ends are rolls 60and 62 which are identified by the leg ends SHAPE DETECTING appearing inFIG. 3 and which are provided to detect the transverse flatness profileof the strip passing to and from the roll flexing units 28 and 30. Thereare several well known types of such measuring devices in the industrysuch as that illustrated and described in US. Pat. Nos. 3,481,194 datedDec. 2, 1969 and 3,499,306 dated Mar. 10, 1970, among others not as wellpublicized. The basic purpose of these units is to determine thetransverse strip profile, i.e., both the magnitude and location of thehills and valleys of non-flatness. Arranged between the rolls 5660 and58-62 are strip deflecting rolls 63 provided to assure proper contactbetween the rolls 56-60 and 5862.

As noted before an important aspect of the invention is to provide amethod and means that will enable the best possible individual orcollective usage of the several corrective forces developed by the units12, 14,, 28, 30, 56, and 58 in removing or reducing the non-flatnessfrom the strip as determined by either or both of the shape detectors 60and 62. With this in mind these corrective forces are correlated andvaried with reference to a given condition of the strip by a mastercontrol computer 64. The control receives signals from the detectorrolls 60 and 62 of the non-flatness of the strip and issues commandsignals to one or more of the units 12, 14, 28, 3t), 56 and 58 as isdetermined to be neces- 'sary to correct totally or in part for theparticular nonflat condition of the strip. The computer control 64 willfollow the typecustomarily provided in the steel industry for stripprocessing equipment, in which as shown in FIG. 2 the control receivessignals from the shape detector rolls 60 and 62 from signal generatingunits 66 and 68 respectively, along with signals of tension values fromthe tension bridles l2 and 14 by signal units 70 and 72 and pressuresignals from the piston cylinder assemblies 46 and 52. It then employsthis data to obtain the best coordinated use of the equipment inremoving totally or in part the non-flatness from the strip.

In briefly describing the operation of the above explained equipment andcontrol let it be assumed as suggested by FIG. 1 that a strip is beingfed through the bridleunits 12 and 14 as it is being processed. Whilethe equipment can be operated in a number of different ways, such as bya feed forward and/or a feed backward control system, semi-automatic orfully automatic, a fully automatic feed forward and feed backward systemwill be described.

As shown in FIG. 1 as the strip passes over the shape detecting roll 60,the signal generator 66 will issue a feed forward signal to the controlunit 64 and cause the effective working forces produced by entry unitsi.e., the bridle 12, deflector roll 56 and the flexing and rolling unit28 to vary if necessary to give the ideal combination of total tension,roll crowning and/or skewing or tilting and mechanical shaping andflex-ing and/or rolling required. As the strip 10, passes over thedelivery shape detecting roll 62 should there still exist anynonflatness a vernier or trim correction will be initiated by a feedbackwards signal from the signal units 68 to the control 64. The controlthen will initiate a trim control signal to one or more of the deliveryunits 30, 58 or E4 to still further reduce or eliminate any non-flatnessin the strip. The control unit will enable the entry and delivery unitsto be always operated in a correlated manner and maintained within adesirable operating range to thus cover a very wide range of entry stripconditions.

In accordance with the provisions of the patent statutes, I haveexplained the principle and operation of my invention and haveillustrated and described what I consider to represent the bestembodiment thereof.

I claim:

' 1. A method of producing flat metallic strip compris ing the steps of:

causing the strip to pass through a controlled elonga- 1 tion zonecreated by two spaced-apart strip tensioning means where the strip issubject to a substantial total tension but below its yield point,causing the strip while subject to said tension to pass around a seriesof strip flexing rolls where the strip is subject to reverse flexingwhereby the tension and flexing imparts a controllable amount ofpermanent elongation to the strip, varying the unit tension transverselyof said strip to vary the transverse unit tension of the portion of thestrip being subject to the flexing operation, determining the transverseflatness profile of the strip when under said tension and between saidtensioning means and changing at least one of said total tension,flexing or unit tension operations to reduce the non-flatness in thestrip.

2. A method of producing flat strip according to claim 1,

wherein said strip flexing step includes subjecting the strip to asimultaneous rolling and flexing operation,

and changing atleast one of said total tension, rolling and flexing orunit tension operations to reduce the non-flatness in the strip issuingfrom said rolling and flexing operation.

3. A method of producing flat metallic strip according to claim I,

wherein said flexing operation includes the step of passing the stripbetween a set of three rolls, one of which is arranged in a nestedrelationship with the others and being of a much smaller diameter thanthe others.

4. A method of producing flat metallic strip according to claim 1,wherein said flexing operating includes the step of passing the stripthrough two succeeding and separate flexing operations whereintheopposite surfaces of the strip are subjected to an equal number oftension-compression steps caused by flexing.

5. A method of producing flat metallic strip according to claim 1wherein said step of varying the unit tension of the strip isaccomplished by varying the length of the path of travel of differentportions of the strip width by manipulation of a deflecting rollarranged to engage one of the surfaces of the strip when subject to saidtotal tension condition.

6. A method of producing flat metallic strip according to claim 5,wherein said variation of length of path of travel is accomplished byapplying a bending mo -.ment to the ends of said deflecting roll.

7. A method of producing flat metallic strip according to claim 5,wherein said variation of length of path of travel is accomplished byapplying a rotation to said deflecting roll about its minor axis.

8. A method of producing flat metallic strip according to claim 1,wherein said determining of the flatness profile of the strip isaccomplished by causing the strip to engage a shape detecting rollarranged on either side of said flexing operation.

9. A method for producing flat metallic strip according to claim 8,wherein said strip is caused to engage said shape detecting rolls on theentry and delivery sides of said flexing operation.

it). A method of producing flat metallic strip according to claim ll,wherein said step of subjecting the strip to a substantial total tensionincludes with respect to said flexing step causing the strip to passbetween entry and delivery tension bridle units.

ill. A method of producing flat metallic strip according to claim 1,wherein said step of subjecting the strip to a substantial total tensionincludes with respect to said flexing step, causing the strip to passbetween entry and delivery tension bridle units,

and wherein said determining of the flatness profile of the strip isaccomplished by causing said strip to engage a shape detecting rollarranged on either side of said flexing operation,

and wherein said step of varying the unit tension of the strip isaccomplished by variation of length of path of travel by manipulation ofa strip deflecting roll arranged to engage one of the surfaces of thestrip when subject to said total tension condition,

and further wherein said flexing operation includes the steps of passingthe strip through two succeeding and separate flexing operations whereinthe opposite surfaces of the strip are subjected to an equal number oftension-compression steps caused by flexing.

12. A method of producing flat metallic strip according to claim ll,wherein said strip flexing operations include subjecting this strip to asimultaneous rolling and flexing operation and changing atleast one ofsaid total tension, rolling and flexing, or unit tension operations toreduce for non-flatness in the strip issuing from said rolling andflexing operation.

13. An apparatus and control for producing flat metallic stripcomprising:

means for passing the strip to a controlled elongation zone,

said elongation zone including two spaced-apart strip tension means forsubjecting the strip to a substantial total tension but below its yieldpoint,

said zone alsoincluding a series of strip flexing roll means constructedand arranged to subject the tensioned strip to reverse flexing wherebythe tension and flexing imparts a controllable amount of permanentelongation to the strip,

a deflector roll arranged to be engaged by said tensioned strip,

means for manipulating said deflector roll to vary the unit tensiontransversely of the strip to thereby vary the transverse unit tension ofthe portion of strip n being subject to the flexing operation, and meansarranged between said tension means for determining the transverseflatness profile of the strip while under said tension and for effectinga change in at least one of said total tension, flexing or unit tensionoperations to reduce the nonflatncss in the strip. 14. An apparatus andcontrol according to claim l3, wherein said flexing roll means includesmeans for bringing said roll means in a rolling and flexing relationshipwith said strip.

15. Apparatus and control according to claim 113, wherein said flexingroll means includes a set of three rolls one of which is arranged in anested relationship with the others and being of a much smaller diameterthan the others.

16. An apparatus and control according to claim 13, wherein said flexingroll means includes two succeeding and separate sets of rollsconstructed and arranged to subject the opposite surfaces of the stripto an equal number of tension-compression steps caused by flexing.

17. An apparatus and control according to claim 13, wherein said meansfor manipulating said deflector roll comprising a means for bending saidroll in order to change its effective crown.

18. An apparatus and control according to claim l3,

wherein said means for manipulating said deflector roll comprises ameans for cocking said roll by applying a rotational force about itsminor axis.

19. An apparatus and control according to claim 13, wherein said meansfor determining the flatness profile of the strip includes a shapedetecting roll arranged on either side of said strip flexing roll means.

20. An apparatus and control according to claim 13, wherein said meansfor subjecting the strip to a total tension includes with respect tosaid flexing roll means, entry and delivery tension bridle units. I

21. An apparatus and control according to claim 13, wherein said meansfor subjecting the strip to a substantial total tension comprises withrespect to said flexing roll means, entry and delivery tension unitbridles,

said means for determining the flatness profile of the strip includes ashape detecting roll arranged on either side of said flexing roll means,

wherein said deflector. roll is arranged to engage one of the surfacesof said strip when subject to said total tension condition,

wherein said flexing roll means includes two succeeding and separatesets of flexing rolls wherein the opposite surfaces of the strip aresubject to an equal number of tension-compression steps caused byflexing,

wherein said flatness profile determining means includes a shapedetecting roll for producing a signal of the non-flatness condition ofthe strip, and

a control unit for receiving said signal from said detecting roll andproducing a command signal to selectively and simultaneously vary one ormore of the operations of said tot-a1 tension, flexing and unit

1. A method of producing flat metallic strip comprising the steps of:causing the strip to pass through a controlled elongation zone createdby two spaced-apart strip tensioning means where the strip is subject toa substantial total tension but below its yield point, causing the stripwhile subject to said tension to pass around a series of strip flexingrolls where the strip is subject to reverse flexing whereby the tensionand flexing imparts a controllable amount of permanent elongation to thestrip, varying the unit tension transversely of said strip to vary thetransverse unit tension of the portion of the strip being subject to theflexing operation, determining the transverse flatness profile of thestrip when under said tension and between said tensioning means andchanging at least one of said total tension, flexing or unit tensionoperations to reduce the non-flatness in the strip.
 2. A method ofproducing flat strip according to claim 1, wherein said strip flexingstep includes subjecting the strip to a simultaneous rolling and flexingoperation, and changing atleast one of said total tension, rolling andflexing or unit tension operations to reduce the non-flatness in thestrip issuing from said rolling and flexing operation.
 3. A method ofproducing flat metallic strip according to claim 1, wherein said flexingoperation includes the step of passing the strip between a set of threerolls, one of which is arranged in a nested relationship with the othersand being of a much smaller diameter than the others.
 4. A method ofproducing flat metallic strip according to claim 1, wherein said flexingoperating includes the step of passing the strip through two succeedingand separate flexing operations wherein the opposite surfaces of thestrip are subjected to an equal number of tension-compression stepscaused by flexing.
 5. A method of producing flat metallic stripaccording to claim 1 wherein said step of varying the unit tension ofthe strip is accomplished by varying the length of the path of travel ofdifferent portions of the strip width by manipulation of a deflectingroll arranged to engage one of the surfaces of the strip when subject tosaid total tension condition.
 6. A method of producing flat metallicstrip according to claim 5, wherein said variation of length of path oftravel is accomplished by applying a bending moment to the ends of saiddeflecting roll.
 7. A method of producing flat metallic strip accordingto claim 5, wherein said variation of length of path of travel isaccomplished by applying a rotation to said deflecting roll about itsminor axis.
 8. A method of producing flat metallic strip according toclaim 1, wherein said determining of the flatness profile of the stripis accomplished by causing the strip to engage a shape detecting rollarranged on either side of said flexing operation.
 9. A method forproducing flat metallic strip according to claim 8, wherein said stripis caused to engage said shape detecting rolls on the entry and deliverysides of said flexing operation.
 10. A method of producing flat metallicstrip according to claim 1, wherein said step of subjecting the strip toa substantial total tension includes with respect to said flexing stepcausing the strip to pass between entry and delivery tension bridleunits.
 11. A method of producing flat metallic strip according to claim1, wherein said step of subjecting the strip to a substantial totaltension includes with respect to said flexing step, causing the strip topass between entry and delivery tension bridle units, and wherein saiddetermining of the flatness profile of the strip is accomplished bycausing said strip to engage a shape detecting roll arranged on eitherside of said flexing operation, and wherein said step of varying theunit tension of the strip is accomplished by variation of length of pathof travel by manipulation of a strip deflecting roll arranged to engageone of the surfaces of the strip when subject to said total tensioncondition, and further wherein said flexing operation includes the stepsof passing the strip through two succeeding and separate flexingoperations wherein the opposite surfaces of the strip are subjected toan equal number of tension-compression steps caused by flexing.
 12. Amethod of producing flat metallic strip according to claim 11, whereinsaid strip flexing operations include subjecting this strip to asimultaneous rolling and flexing operation and changing atleast one ofsaid total tension, rolling and flexing, or unit tension operations toreduce for non-flatness in the strip issuing from said rolling andflexing operation.
 13. An apparatus and control for producing flatmetallic strip comprising: means for passing the strip to a controlledelongation zone, said elongation zone including two spaced-apart striptension means for subjecting the strip to a substantial total tensionbut below its yield point, said zone also including a series of stripflexing roll means constructed and arranged to subject the tensionedstrip to reverse flexing whereby the tension and flexing imparts acontrollable amount of permanent elongation to the strip, a deflectorroll arranged to be engaged by said tensioned strip, means formanipulating said deflector roll to vary the unit tension transverselyof the strip to thereby vary the transverse unit tension of the portionof strip being subject to the flexing operation, and means arrangedbetween said tension means for determining the transverse flatnessprofile of the strip while under said tension and for effecting a changein at least one of said total tension, flexing or unit tensionoperations to reduce the non-flatness in the strip.
 14. An apparatus andcontrol according to claim 13, wherein said flexing roll means includesmeans for bringing said roll means in a rolling and flexing relationshipwith said strip.
 15. Apparatus and control according to claim 13,wherein said flexing roll means includes a set of three rolls one ofwhich is arranged in a nested relationship with the others and being ofa much smaller diameter than the others.
 16. An apparatus and controlaccording to claim 13, wherein said flexing roll means includes twosucceeding and separate sets of rolls constructed and arranged tosubject the opposite surfaces of the strip to an equal number oftension-compression steps caused by flexing.
 17. An apparatus andcontrol according to claim 13, wherein said means for manipulating saiddeflector roll comprising a means for bending said roll in order tochange its effective crown.
 18. An apparatus and control according toclaim 13, wherein said means for manipulating said deflector rollcomprises a means for cocking said roll by applying a rotational forceabout its minor axis.
 19. An apparatus and control according to claim13, wherein said means for determining the flatneSs profile of the stripincludes a shape detecting roll arranged on either side of said stripflexing roll means.
 20. An apparatus and control according to claim 13,wherein said means for subjecting the strip to a total tension includeswith respect to said flexing roll means, entry and delivery tensionbridle units.
 21. An apparatus and control according to claim 13,wherein said means for subjecting the strip to a substantial totaltension comprises with respect to said flexing roll means, entry anddelivery tension unit bridles, said means for determining the flatnessprofile of the strip includes a shape detecting roll arranged on eitherside of said flexing roll means, wherein said deflector roll is arrangedto engage one of the surfaces of said strip when subject to said totaltension condition, wherein said flexing roll means includes twosucceeding and separate sets of flexing rolls wherein the oppositesurfaces of the strip are subject to an equal number oftension-compression steps caused by flexing, wherein said flatnessprofile determining means includes a shape detecting roll for producinga signal of the non-flatness condition of the strip, and a control unitfor receiving said signal from said detecting roll and producing acommand signal to selectively and simultaneously vary one or more of theoperations of said total tension, flexing and unit tension means.